Report-2 - Dimmer as a Variac.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi All,

To follow up on my last report...

I hooked up the high voltage probe to the output of the NST with nothing
else but the protection filter.  The scope picture is at:

http://hot-streamer-dot-com/temp/Tek00007.gif

As I thought, the NST output voltage mirrors the input voltage.  For some
reason, the waveform is not symmetrical with respect to the positive and
negative part of the cycle.

I then hooked up a primary circuit and powered up the coil but without the
gap firing:

http://hot-streamer-dot-com/temp/Tek00008.gif

A very nice NST output voltage waveform!  The input is "interesting" but
nothing there that seems to hurt anything.

I then fired the primary gap which was acting as a static gap in this case"

http://hot-streamer-dot-com/temp/Tek00009.gif

This waveform is time averaged so some detail is missing but nothing
concerning here.

I then looked back at the current into the coil:

http://hot-streamer-dot-com/temp/Tek00010.gif

A non averaged picture is at:

http://hot-streamer-dot-com/temp/Tek00013.gif

This looks very much like a async static gap coil on a variac.  The scope
reported high spikes but those were probably radiated noise on tonight's
impromptu test setup.

So it looks like you can't use PFC caps and I think the dimmer would mess
up a sync gap system since it changes the dwell of the signals.  Perhaps
John's sync gap controller would help but you would be doing a lot of
chasing I would think and that needs a variac itself anyway.  There is some
noise hash in there but it is not too bad.

It looks like it may work well on a lower powered static gap system which
is what most people without a variac probably have anyway.  The primary cap
size may differ from the usual too with a dimmer.  Even with premium
electrical parts and the box, cord, front plate... it only cost me $30.
With the cheapest parts and a little digging, one could probably make it
for only $10.  If it would work, that would be a very attractive option for
the beginner or first time coiler that does not have a variac and has a
simple lower power coil.

Still far from ready for general use, but the preliminary results are
encouraging!  Aside from remounting the triac (the copper on aluminium
grounding rivet was loose anyway :o)), the dimmer is unchanged.

Cheers,

	Terry